Multi site communication systems provide wide-area coverage for users of the system. These systems comprise a number of sites, with each site corresponding to a different geographic coverage area and each site having located therein an infrastructure device (which will hereinafter be referred to as a repeater or Base Repeater, BR) serving the coverage area by managing one or more channels in the coverage area. Accordingly, for purposes of the teachings herein, a site is characterized by a repeater that serves a particular coverage area, a channel for wireless communication device transmissions, and a system identification that identifies transmissions from the repeater on the channel at the site. Some or all of the infrastructure devices in a multi site communication system may be networked or connected together via a backend network to provide the wide-area coverage via one or more logical wide-area channels, and in many instances two or more of the coverage areas have some degree of overlap. A backend network may comprise a T-1 link, point to point microwave, private internet, or public internet, for example.
Multi site communication systems may be designed as trunked systems or conventional systems. In trunked systems, a limited number of communication channels are shared among a much larger number of users to facilitate efficient use of the system's communication resources. Thus, to afford each user a reasonable opportunity to use the system's resources, one or more control channels are utilized by the infrastructure to allocate the shared resources between the many users in the system. In general, when a wireless communication device (which will hereinafter be referred to as a radio) wants to communicate on the trunked system, it sends a request on the control channel to communicate with another radio or group of radios. In turn, the requesting radio (and the radios to which it desires to communicate) receives back on the control channel the allocation of a traffic channel to use for their communications. Upon the conclusion of the communications, the allocated channel is released for use by other radios in the system.
In conventional systems, a number of communication channels are also shared amongst a number of users (although the number of users per channel is typically much smaller than in trunked systems). However, there is no control mechanism provisioned in the infrastructure to allocate the resources among the users in the system. Thus, in contrast to a trunked system, each channel in a conventional system is dedicated to one or more groups of users enabling the users to control access to the channels through their radios by manually selecting a channel or selecting a talkgroup that is assigned a particular channel in order to start a communication session and transmit and receive media during the session.
When a communication device such as a subscriber unit or a repeater is transmitting communications, there may be instances when interrupting the communication device may be important and/or beneficial. For example, a first police officer needing back up may need to interrupt a second police officer that is engaged in a call. In such an instance, it would be important to have a mechanism to interrupt the second police officer to notify the second officer that the first police officer requires assistance.
Accordingly, there is a need for a method for interrupting voice transmissions within a multi site communication system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.